I don't enjoy working Sundays. For some reason all the crazy weird people come on Sundays.
I have narrowed the reasons for it down to:
  • Nobody in a rush
  • Fewer people wanting service
We all have limited time on this planet before we die. One of the most simple and subtle ways of respecting one another is being aware of taking up someone else's time. Make it necessary, where both people can benefit. Of course, I'm stuck here until the end of my shift and I am paid for it.
A combination of lack of societal pressure in a normal peak queue with social proof and people having longer before they need to leave, creates a perfect storm, where bored imbeciles approach to ask silly meaningless questions, troll or make a simple transaction seriously dragged out. It can even be regulars in the week that have their go-to drink but because their train is not for another 50 minutes, decide to navigate through pretty much all customisation options but in the end choose that same regular drink - even when offered a complimentary alternative drink if they didn't like the modification - a good chance to try something new without any risk. Always declined!

I'm all for interesting people coming forward to have a chat. It is very much needed when all tasks have been completed and there is nobody to serve. But we just end up with someone wanting to go through all the syrups for sweetness... they are ALL sweet, sugar-free options have sweeteners, people asking about menu items with zero enthusiasm or interest as a time filler... and the same applies for when people ask about merchandise options.

Then there are those that resort to abuse - customers or not. 
Starbucks is a social proof business, nobody really wants to be first in line, but once someone is there, everyone joins the queue... and most reasonable people won't tolerate someone ahead of them delaying their order, it takes someone with sheer audacity to try this during peak or intermediate periods of time, so it doesn't often occur.